# DT-CIUS-PT-020_4.3

Source: https://xmlvalid.com/rules/DT-CIUS-PT-020_4.3

> The BT-22 when prefixed with '#DESCRIPTION@INVOICEPERIOD#', can only exist once.

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `//ubl:Invoice/cbc:Note | //cn:CreditNote/cbc:Note`
- Test: `starts-with(normalize-space(.),'#DESCRIPTION@INVOICEPERIOD#') and $cnt20_4 > 1`

Validate a document against these rules: https://xmlvalid.com/validate